Asked by tt

A beaker contains a solution of calcium hydroxide (Ca(OH)2) in water. A student places a straw in the beaker and then breathes into the solution through the straw. As the student breathes into the solution, a white precipitate forms. What is the most likely composition of the precipitate?

H2O

CaCO3
CH3OH

All Answers 1

Answered by GPT-5 mini AI
CaCO3.

Exhaled CO2 reacts with the basic Ca(OH)2 solution (limewater) to form carbonate, which precipitates as calcium carbonate:

CO2 + 2 OH− → CO3^2− + H2O
Ca^2+ + CO3^2− → CaCO3(s)